X-ray generating device and x-ray photography system

ABSTRACT

An X-ray generating device includes an X-ray tube, an X-ray tube drive circuit, an electron acceleration voltage generation circuit, and a control unit communicating with the drive circuit and the voltage generation circuit, the X-ray tube, the drive circuit, and the voltage generation circuit are arranged inside a storage container filled with an insulating oil, a path connecting the drive circuit and the control unit includes an optical fiber cable arranged inside the storage container, the optical fiber cable has a coating that suppresses fluctuation due to a convective flow of the insulating oil, the coating is cured by, from a resin material containing a plasticizer, a part of the plasticizer being leaching out, and the control unit is configured to facilitate leaching of the plasticizer by driving the voltage generation circuit to apply a voltage to the optical fiber cable in a state of no X-ray being generated.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of InternationalApplication PCT/JP2016/004908 filed on Nov. 17, 2016 and designated theU.S., the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to an X-ray generating device and an X-rayphotography system.

BACKGROUND ART

An X-ray photography system is known as one of industrial nondestructiveinspection devices. For example, an X-ray inspection device having amicro-focus X-ray tube is used for inspection of electronic devicesrepresented by semiconductor integrated circuit substrates. An X-raytube is an X-ray source that emits an X-ray from a target by applying,between an anode and a cathode, a high voltage with a predeterminedpotential difference in accordance with an X-ray energy to irradiate thetarget with electrons accelerated by the high voltage. A micro-focusX-ray tube is an X-ray tube having a plurality of grid electrodes on thecathode side and has a function of converging the orbit of an electronbeam by controlling an electrostatic lens with the voltage applied tothese grid electrodes.

In an X-ray generating device using a micro-focus X-ray tube,improvement of a grounding scheme of the X-ray tube, a supplying methodof a control signal, or the like has been made to address the need forcontrolling the voltage applied to the grid electrodes. For example, anX-ray generating device disclosed in Japanese Patent ApplicationPublication No. 2003-317996 is configured such that the control signalof the grid voltage applied to grid electrodes is supplied through anoptical fiber cable, and thereby a negative high voltage can be appliedto the cathode of the X-ray tube. Further, a neutral grounding scheme inwhich an enclosure of the X-ray tube is grounded and a positive highvoltage and a negative high voltage are applied to the anode and thecathode is employed, and thereby the voltage applied between theenclosure and the anode is reduced by around half.

In terms of easy handling or the like when installing an X-raygenerating device in an X-ray photography system, there is a demand fora reduction in size of the X-ray generating device. Further, in terms ofa higher penetrating power, there is a demand for an increase in thevoltage applied to an X-ray tube. However, study by the inventors of thepresent application has first revealed that an advancement of reductionin size of the X-ray generating device or increase in the applicationvoltage may increase malfunction of a control system.

SUMMARY OF INVENTION

An object of the present invention is to provide an X-ray generatingdevice which can suppress malfunction of the control system due to theadvancement of reduction in size or increase in the application voltage.Further, another object of the present invention is to provide areliable X-ray photography system which can stably acquire capturedimages by using such the X-ray generating device.

According to an aspect of the present invention, there is provided anX-ray generating device including an X-ray tube, a drive circuit thatdrives the X-ray tube, a voltage generation circuit that generates anelectron acceleration voltage applied to the X-ray tube, and a controlunit that communicates with the drive circuit and the voltage generationcircuit, wherein at least the X-ray tube, the drive circuit, and thevoltage generation circuit are arranged inside a storage containerfilled with an insulating oil, wherein at least a part of a pathconnecting the drive circuit and the control unit is formed of anoptical fiber cable arranged inside the storage container, wherein theoptical fiber cable has a coating that suppresses fluctuation of theoptical fiber cable due to a convective flow of the insulating oilgenerated at driving of the voltage generation circuit, wherein thecoating is cured by, from a resin material containing a plasticizer, atleast apart of the plasticizer being leaching out, and wherein thecontrol unit is configured to facilitate leaching of the plasticizer bydriving the voltage generation circuit to apply a voltage for apredetermined time to the optical fiber cable in a state of no X-raybeing generated.

Further, according to another aspect of the present invention, there isprovided a method of manufacturing an X-ray generating device includingan X-ray tube, a drive circuit that drives the X-ray tube, a voltagegeneration circuit that generates an electron acceleration voltageapplied to the X-ray tube, and a control unit that communicates with thedrive circuit and the voltage generation circuit, wherein at least theX-ray tube, the drive circuit, and the voltage generation circuit arearranged inside a storage container filled with an insulating oil, andwherein at least apart of a path connecting the drive circuit and thecontrol unit is formed of an optical fiber cable arranged inside thestorage container, the method including installing the X-ray tube, thedrive circuit, the voltage generation circuit, and the optical fibercable inside the storage container, filling the insulating oil in thestorage container, and curing, after filling the insulating oil in thestorage container, a coating of the optical fiber cable by driving thevoltage generation circuit, without driving the drive circuit, to applya voltage for a predetermined time to the optical fiber cable having thecoating of a resin material containing a plasticizer and causing theplasticizer to leach out from the coating.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating a general configuration of anX-ray generating device according to a first embodiment of the presentinvention;

FIG. 2 is a schematic diagram illustrating an example of a configurationof an optical fiber cable;

FIG. 3 is a flowchart illustrating a method of manufacturing the X-raygenerating device according to the first embodiment of the presentinvention;

FIG. 4 is a schematic diagram illustrating an example of a configurationof an optical fiber cable of X-ray generating devices according tosecond and third embodiments of the present invention;

FIG. 5 is a flowchart illustrating a method of manufacturing the X-raygenerating devices according to the second and third embodiments of thepresent invention; and

FIG. 6 is a block diagram illustrating a general configuration of anX-ray photography system according to a fourth embodiment of the presentinvention.

DESCRIPTION OF EMBODIMENTS First Embodiment

An X-ray generating device according to a first embodiment of thepresent invention will be described with reference FIG. 1 to FIG. 3.FIG. 1 is a block diagram illustrating the general configuration of theX-ray generating device according to the present embodiment. FIG. 2 is aschematic diagram illustrating an example of the configuration of anoptical fiber cable. FIG. 3 is a flowchart illustrating a method ofmanufacturing the X-ray generating device according to the presentembodiment.

First, the configuration of the X-ray generating device according to thepresent embodiment will be described by using FIG. 1 and FIG. 2.

As illustrated in FIG. 1, an X-ray generating device 100 according tothe present embodiment includes an X-ray tube 20, a high voltagegeneration circuit 30, an electron gun drive circuit 40, and a controlunit 50. At least the X-ray tube 20, the high voltage generation circuit30, and the electron gun drive circuit 40 of the above components arearranged inside a storage container 10. The storage container 10 isfilled with an insulating oil 80 in order to ensure a dielectricwithstand voltage among respective components arranged in the storagecontainer 10. An electric insulating oil such as a mineral oil, asilicone oil, a fluorine-base oil, or the like is preferable as theinsulating oil 80. A mineral oil, which is easily handled, is preferablyapplied to an X-ray generating device with the X-ray tube 20 whose ratedtube voltage is around 100 kV.

The X-ray tube 20 includes an electron source 22, a grid electrode 26,and an anode 28. The electron source 22 and the grid electrode 26 areconnected to the electron gun drive circuit 40 and applied with desiredcontrol voltages, respectively. The anode 28 is connected to the storagecontainer 10 maintained at a ground potential. A target (notillustrated) that generates an X-ray by irradiation of an electron beamis provided to the anode 28. Note that, although only the single gridelectrode 26 is depicted in FIG. 1, a plurality of grid electrodes 26are typically provided.

While the electron source 22 is not limited in particular, a hot cathodesuch as a tungsten filament or an impregnated cathode or a cold cathodesuch as a carbon nanotube, or the like may be applied thereto, forexample. The material forming a target is preferably a material having ahigh melting point and a high X-ray generation efficiency, and atungsten, a tantalum, a molybdenum, an alloy thereof, or the like may beapplied thereto, for example. Note that, the electron source 22 and thegrid electrode 26 may be collectively referred to as “electron gun” inthe present specification.

An X-ray is emitted from the target by accelerating electrons emittedfrom the electron source 22 by a high voltage between the electronsource 22 and the anode 28 to cause the accelerated electrons to collidewith the target provided on the anode 28. The amount of X-ray emittedfrom the target can be controlled by using the amount of the electronbeam irradiated to the target, that is, the supplied current in the caseof the hot-cathode type electron source 22. The orbit of the electronbeam irradiated to the target can be controlled by using the gridvoltage applied to the grid electrode 26. In this sense, the electronsource 22 and the grid electrode 26 forma control mechanism thatcontrols the electron beam emitted from the electron gun.

The high voltage generation circuit 30 includes a step-up transformer 32and a step-up circuit 34. The step-up circuit 34 may be a Cockcroftcircuit, for example. The high voltage generation circuit 30 generates anegative high voltage against the storage container 10 maintained at theground potential. The high voltage generation circuit 30 is connected tothe electron gun drive circuit 40.

The electron gun drive circuit 40 includes a rectifier circuit 42, alogic circuit 44, an electron source drive circuit 46, and a gridvoltage control circuit 48. The rectifier circuit 42 is connected to thelogic circuit 44, the electron source drive circuit 46, and the gridvoltage control circuit 48. Thereby, a voltage supplied to the rectifiercircuit 42 via a high insulating transformer 36 is rectified, and therectified voltage can be supplied to the logic circuit 44, the electronsource drive circuit 46, and the grid voltage control circuit 48. One ofthe input terminals of the rectifier circuit 42 is connected to theoutput terminal of the high voltage generation circuit 30. That is, ineach circuit of the electron gun drive circuit 40, the negativepotential supplied from the high voltage generation circuit 30 is usedas a reference potential of the electron gun drive circuit 40.

The electron source drive circuit 46 controls the voltage or the currentsupplied to the electron source 22 in accordance with a control signalsupplied from a control circuit 52 via the logic circuit 44. The gridvoltage control circuit 48 controls a grid voltage supplied to the gridelectrode 26 in accordance with a control signal supplied from a controlcircuit 52 via the logic circuit 44.

The control unit 50 includes the control circuit 52 and an invertercircuit 54. The control circuit 52 is connected to the electron gundrive circuit 40 and the inverter circuit 54. The inverter circuit 54includes an inverter 56 connected to the step-up transformer 32 arrangedinside the storage container 10 and an inverter 58 connected to the highinsulating transformer 36 arranged inside the storage container 10. Thecontrol circuit 52 supplies predetermined control signals to theelectron gun drive circuit 40 and the inverter circuit 54. The invertercircuit 54 controls the inverters 56 and 58 in accordance with thecontrol signal supplied from the control circuit 52 and suppliespredetermined drive voltages to the step-up transformer 32 and the highinsulating transformer 36. The control circuit 52 monitors an outputvoltage of the high voltage generation circuit 30 and adjusts the drivevoltage of the step-up transformer 32 by using the control signalsupplied to the inverter circuit 54 such that the output voltage of thehigh voltage generation circuit 30 becomes a predetermined voltage.

As illustrated in FIG. 1, the control unit 50 and the high voltagegeneration circuit 30 are connected via the step-up transformer 32, thatis, insulated from each other. Similarly, the control unit 50 and theelectron gun drive circuit 40 are connected via the high insulatingtransformer 36, that is, insulated from each other. In an example, thecontrol unit 50 is connected to the ground potential. Further, theelectron gun drive circuit 40 is connected to the high voltagegeneration circuit 30. Therefore, a potential corresponding to anegative high voltage generated at the high voltage generation circuit30 via the step-up transformer 32 occurs between the control unit 50 andthe electron gun drive circuit 40. That is, an electric field occursbetween the control unit 50 and the electron gun drive circuit 40.

Among paths responsible for mutual communication between the controlcircuit 52 and the electron gun drive circuit 40, at least a part of thepaths within the storage container 10 is formed of an optical fibercable 60 in order to maintain electric insulation. This enables acontrol signal from the control circuit 52, which operates based on theground potential as the reference potential, to control the electronsource drive circuit 46 and the grid voltage control circuit 48 withinthe electron gun drive circuit 40, which operates based on the negativepotential supplied from the high voltage generation circuit 30 as thereference voltage. The optical fiber cable 60 is connected to thecontrol circuit 52 and the logic circuit 44 via a photoelectricconversion device 78. Note that the reference potential is a potentialthat is defined as a reference in each circuit.

Here, in the X-ray generating device 100 according to the presentembodiment, the coating material of the optical fiber cable 60 is formedof a material that has a sufficient rigidity for suppressing fluctuationof the optical fiber cable 60 due to a convective flow of the insulatingoil 80 when the X-ray generating device 100 is driven.

As discussed above, the advancement of reduction in size or increase inan application voltage of the X-ray generating device has revealed anissue of malfunction of a control system in which the control circuit 52controls the electron source drive circuit 46 or the grid voltagecontrol circuit 48. Study by the inventors has found that one of thereasons of such malfunction is an increased fluctuation of an opticalfiber cable caused by an increased convective flow of the insulating oil80 at driving due to the reduction in size or the increase in theapplication voltage of the device.

When a high voltage is applied to the X-ray tube 20 from the highvoltage generation circuit 30 inside the storage container 10 filledwith the insulating oil 80, the insulating oil 80 around the highvoltage generation circuit 30 is locally charged and convectively flowsdue to Electro Hydro Dynamics (EHD) effect. This convective flowincreases as the electric field intensity increases, that is, as thereduction in size or the increase in the application voltage of theX-ray generating device is advanced. A faster flow speed of theinsulating oil 80 results in larger fluctuation of the soft opticalfiber cable 60, which may cause a communication error between thecontrol unit 50 and the electron gun drive circuit 40 in some cases.Since such a convective flow of the insulating oil 80 occurs at randominside the storage container 10, it is difficult to suppress aninfluence of the convective flow by improving the position of theoptical fiber cable 60.

From this point of view, in the X-ray generating device according to thepresent embodiment, the coating material of the optical fiber cable 60is formed of a material having a rigidity which can sufficientlysuppress the fluctuation of the optical fiber cable 60 due to aconvective flow of the insulating oil 80 when the X-ray generatingdevice 100 is driven. If the optical fiber cable 60 is not flexible inthe manufacturing of the X-ray generating device 100, however,installation of various components or connection of the optical fibercable 60 to the inside of the storage container 10 will be difficult,which may be expected to be an obstacle to assembling.

Thus, in the X-ray generating device according to the presentembodiment, the coating material of the optical fiber cable 60 is formedof a material which is flexible at assembling but is able to be cured inthe subsequent process. Then, the fluctuation of the optical fiber cable60 due to a convective flow of the insulating oil 80 is suppressed bycuring the coating material to enhance the rigidity of the optical fibercable 60 after assembling. The coating material of the cured opticalfiber cable 60 is configured such that the form of the optical fibercable 60 when the high voltage generation circuit 30 is driven ismaintained to substantially the same form as the form of the opticalfiber cable 60 when the high voltage generation circuit 30 is notdriven. Substantially the same form means that an influence such as anoccurrence rate of communication errors, for example, on a signalpropagating in the optical fiber cable 60 does not change between theform when the high voltage generation circuit 30 is driven and the formwhen the high voltage generation circuit 30 is not driven.

In the present embodiment, a resin material containing a plasticizer isused as a coating material of the optical fiber cable 60 having theabove characteristics. The resin material containing a plasticizer losesflexibility and is cured by leaching of the plasticizer. By assemblingthe X-ray generating device in a state where the resin material formingthe coating material of the optical fiber cable 60 contains theplasticizer and is still flexible and then removing the plasticizer forcuring, it is possible to enhance the rigidity of the optical fibercable 60 at driving of the X-ray generating device without obstructingthe assembling.

Note that leaching of a plasticizer added to a resin material is knownand such a plasticizer is made so as not to leach out in general. Incontrast, in the present invention, by intentionally allowing aplasticizer added to a resin material to leach out in an insulating oil,the optical fiber cable 60 is cured to suppress fluctuation of theoptical fiber cable 60 due to a convective flow of the insulating oil80.

As illustrated in FIG. 2, for example, the optical fiber cable 60 has anelement optical fiber 70 in which an optical fiber 66 comprising a core62 and a clad 64 is covered with a resin member 68, a primary coating 72made of tensile strength fibers such as glass fibers, and a secondarycoating 74 made of a resin material. In such the optical fiber cable 60,the secondary coating 74 as an outer jacket can be formed of a resinmaterial containing a plasticizer. Alternatively, an outer jacket (thesecondary coating 74) of the optical fiber cable 60 may be coated with aresin material containing a plasticizer.

The resin material forming a coating member of the optical fiber cable60 is not limited in particular, and a polyvinyl chloride resin may beapplied thereto, for example. Further, a plasticizer added to a resinmaterial is not limited in particular as long as it may facilitateleaching from the resin material by a process described later. Forexample, DEHP (dioctyl phthalate), DINP (diisononyl phthalate), or thelike of phthalic esters may be applied as a plasticizer added to thepolyvinyl chloride resin.

Since a rigidity required to the optical fiber cable 60 depends on aflow rate of the insulating oil 80 that varies in accordance with avoltage applied to the X-ray tube 20, a length of the optical fibercable 60, or the like, the rigidity cannot be defined in the same way.It is desirable to see the flow rate of the insulating oil 80 at drivingin advance and select a coating member of the optical fiber cable asappropriate so that the rigidity which does not cause fluctuation atthis time is achieved by the cured optical fiber cable 60. The rigidityof the cured optical fiber cable can be adjusted by a resin material, athickness of a coating, an amount of a plasticizer added in advance, orthe like, for example. Note that, in the present specification, arigidity which does not cause fluctuation of the optical fiber cable 60means a rigidity sufficient for preventing a communication error in thecommunication through the optical fiber cable 60. Fluctuation of theoptical fiber cable 60 is not required to be completely prevented aslong as no communication error due to fluctuation of the optical fibercable 60 occurs.

A method of applying a high voltage to the optical fiber cable 60 in theinsulating oil 80 may preferably be used as a method of removing aplasticizer from a resin material forming a coating member of theoptical fiber cable 60 for curing. Study by the inventors has found thatapplication of a high voltage to a resin material containing aplasticizer in an insulating oil facilitates leaching of the plasticizerfrom the resin material. That is, application of a voltage for apredetermined time to the optical fiber cable 60 inside a storagecontainer filled with the insulating oil 80 allows the optical fibercable 60 to be cured.

As described above, in the X-ray generating device according to thepresent embodiment, at operation, a potential difference occurs betweenthe electron gun drive circuit 40 and the control circuit 52 on theconnection path of the optical fiber cable 60. Since a potentialdifference between the electron gun drive circuit 40 and the controlcircuit 52 causes a voltage to be applied to the optical fiber cable 60therebetween, this voltage can facilitate leaching of the plasticizerfrom the resin material of the optical fiber cable 60. That is, in theX-ray generating device according to the present embodiment, the coatingmember of the optical fiber cable 60 can be cured by utilizing thefunction of the X-ray generating device as it stands without using anyadditional solution.

Next, a method of manufacturing the X-ray generating device according tothe present embodiment will be described by using FIG. 3. The X-raygenerating device according to the present embodiment can bemanufactured according to a flow illustrated in FIG. 3.

First, respective components of the X-ray generating device are prepared(step S101). In this step, an optical fiber cable formed of a resinmaterial whose coating member contains a plasticizer is prepared as theoptical fiber cable 60.

Subsequently, among the prepared components, those to be accommodated inthe storage container 10 are installed inside the storage container 10(step S102). In this step, since the optical fiber cable 60 has acoating member formed of the resin material containing the plasticizerand is flexible, installation of respective components and connection ofthe optical fiber cable 60 can be easily made.

Subsequently, the insulating oil 80 is filled in the storage container10 (step S103). It is preferable to apply vacuum impregnation, in whichthe insulating oil 80 is injected into the storage container 10 afterevacuating the inside of the storage container 10, to fill theinsulating oil 80 in the storage container 10.

Subsequently, after the completion of assembling of the X-ray generatingdevice, the high voltage generation circuit 30 is driven, and apotential difference is generated between the electron gun drive circuit40 and the control circuit 52. This potential difference causes avoltage to be applied to the optical fiber cable 60, the plasticizerleaches out from the resin material of the coating of the optical fibercable 60, and the coating of the optical fiber cable 60 is cured (stepS104). The curing process of the coating of the optical fiber cable 60can be performed at the same time as driving for aging of the X-raygenerating device or inspection of the function of respectivecomponents.

The voltage applied between the electron gun drive circuit 40 and thecontrol circuit 52 in performing the curing process of the optical fibercable 60 is not necessarily required to be the same as the voltageapplied between the electron gun drive circuit 40 and the controlcircuit 52 in generating an X-ray. The voltage applied between theelectron gun drive circuit 40 and the control circuit 52 can be set asappropriate to values suitable for the curing of the optical fiber cable60 and the generation of the X-ray, respectively.

Further, in the curing process of the optical fiber cable 60, not wholeof the plasticizer contained in the coating of the optical fiber cable60 is required to leach out. The hardness of the coating generallyincreases as the plasticizer leaches out, and thus leaching of only apart of the plasticizer may allow for a desired rigidity. In this case,the plasticizer may remain in the coating after the curing process. Inthis case, it may be preferable to perform the curing process of theoptical fiber cable 60 while monitoring fluctuation (hardness) of theoptical fiber cable 60 and stop the curing process when a desiredhardness is exceeded.

Although time required to the curing process of the optical fiber cable60 may not be defined in the same way because it varies in accordancewith a voltage applied to the optical fiber cable 60, compositions ofthe coating, or the like, the time is typically around several hours.During this curing process, the X-ray generating device may becontrolled to stop generating X-ray. For a curing process of the opticalfiber cable 60, a drive mode in which the high voltage generationcircuit 30 is driven in a state of no X-ray being generated may beimplemented as a drive mode of the X-ray generating device performedunder the control of the control unit 50.

Note that a state of no X-ray being generated can be controlled by avoltage applied to the grid electrode 26, for example. For example,switching of the voltage applied to the grid electrode 26 allowselectrons generated by the electron source 22 to stay between theelectron source 22 and the grid electrode 26 or to reach the anode. Inthis case, a state of no X-ray being generated can be realized by thecontrol that causes electrons to stay between the electron source 22 andthe grid electrode 26.

By curing the coating of the optical fiber cable 60 as discussed above,it is possible to suppress fluctuation of the optical fiber cable 60 dueto a convective flow of the insulating oil 80 at the operation of theX-ray generating device and prevent malfunction of the control system.

As discussed above, according to the present embodiment, since therigidity of the optical fiber cable 60 is increased and fluctuation ofthe optical fiber cable 60 due to a convective flow of the insulatingoil 80 is suppressed, malfunction of the control system can be reduced.This allows for a further reduction in size of the X-ray generatingdevice and a further increase in the application voltage.

Second Embodiment

An X-ray generating device according to a second embodiment of thepresent invention will be described with reference to FIG. 4 and FIG. 5.The same components as those of the first embodiment are labeled withthe same reference numerals, and the description thereof will be omittedor simplified. FIG. 4 is a schematic diagram illustrating the structureof an optical fiber cable of the X-ray generating device according tothe present embodiment. FIG. 5 is a flowchart illustrating a method ofmanufacturing the X-ray generating device according to the presentembodiment.

The X-ray generating device according to the present embodiment is thesame as the X-ray generating device of the first embodiment except thedifference of the configuration of the optical fiber cable 60. That is,in the X-ray generating device according to the present embodiment, acoating made of an epoxy resin is provided on the outer circumference ofthe optical fiber cable 60.

The epoxy resin is a thermoplastic resin that is cured when mixed with acuring agent. While a thermoplastic resin has a flexibility immediatelyafter an epoxy resin and a curing agent are mixed, the thermoplasticresin has a rigidity that can withstand fluctuation of the optical fibercable 60 due to a convective flow of the insulating oil 80 as it iscured with elapsed time. Further, the cured epoxy resin has an oilresistance and would not be softened in reaction with the insulating oil80. Therefore, by coating the optical fiber cable 60 with an epoxyresin, it is possible to suppress fluctuation of the optical fiber cable60 due to a convective flow of the insulating oil 80 at the operation ofthe X-ray generating device and to prevent malfunction of the controlsystem.

A coating 76 made of an epoxy resin may be provided so as to cover theouter jacket (the secondary coating 74) of the optical fiber cable 60 asillustrated in FIG. 4, for example, or may be provided as an outerjacket (for example, the secondary coating 74) of the optical fiber 66.The epoxy resin coating 76 is not necessarily required to be provided onthe entire outer circumference of the optical fiber cable 60 as long asit provides a desired rigidity to the optical fiber cable 60. Further,the epoxy resin coating 76 is not necessarily required to be providedover the entire length of the optical fiber cable 60.

Next, a method of manufacturing the X-ray generating device according tothe present embodiment will be described by using FIG. 5. The X-raygenerating device according to the present embodiment can bemanufactured according to a flow illustrated in FIG. 5.

First, respective components of the X-ray generating device are prepared(step S201).

Subsequently, among the prepared components, those to be accommodated inthe storage container 10 are installed inside the storage container 10(step S202). In this step, the optical fiber cable 60 is installed to apredetermined location in the storage container 10 after an epoxy resincoating mixed with a curing agent is applied thereto and before thisepoxy resin is cured. Since the optical fiber cable 60 is flexiblebefore the epoxy resin is cured, installation of respective componentsand connection of the optical fiber cable 60 can be easily made.

The epoxy resin coating provided on the optical fiber cable is cured ascrosslink networking by an epoxy group develops with elapsed time (stepS203).

Subsequently, after the epoxy resin is cured, the insulating oil 80 isfilled in the storage container 10 (step S103). It is preferable toapply vacuum impregnation, in which the insulating oil 80 is injectedinto the storage container 10 after evacuating the inside of the storagecontainer 10, to fill the insulating oil 80 in the storage container 10.

By curing the optical fiber cable 60 as discussed above, it is possibleto suppress fluctuation of the optical fiber cable 60 due to aconvective flow of the insulating oil 80 at the operation of the X-raygenerating device and prevent malfunction of the control system.

As discussed above, according to the present embodiment, since therigidity of the optical fiber cable 60 is increased and fluctuation ofthe optical fiber cable 60 due to a convective flow of the insulatingoil 80 is suppressed, malfunction of the control system can be reduced.This allows for a further reduction in size of the X-ray generatingdevice and a further increase in the application voltage.

Third Embodiment

An X-ray generating device according to a third embodiment of thepresent invention will be described with reference to FIG. 5. The samecomponents as those of the first and second embodiments are labeled withthe same reference numerals, and the description thereof will be omittedor simplified. FIG. 5 is a flowchart illustrating a method ofmanufacturing the X-ray generating device according to the presentembodiment.

The X-ray generating device according to the present embodiment is thesame as the X-ray generating device of the first and second embodimentsexcept the difference of the configuration of the optical fiber cable60. That is, in the X-ray generating device according to the presentembodiment, a coating made of a photo-curing resin is provided on theouter circumference of the optical fiber cable 60.

The photo-curing resin is a resin material that is cured by irradiationof an energy ray such as an ultraviolet ray or the like. While aphoto-curing resin has a flexibility before irradiation of an energyray, a cured photo-curing resin has a sufficient rigidity to suppressfluctuation of the optical fiber cable 60 due to a convective flow ofthe insulating oil 80. Therefore, by coating the optical fiber cable 60with a photo-curing resin, it is possible to suppress fluctuation of theoptical fiber cable 60 due to a convective flow of the insulating oil 80at the operation of the X-ray generating device and to preventmalfunction of the control system.

A coating 76 made of a photo-curing resin may be provided so as to coverthe outer jacket (the secondary coating 74) of the optical fiber cable60 as illustrated in FIG. 4, for example, or may be provided as an outerjacket (for example, the secondary coating 74) of the optical fiber 66.The photo-curing resin coating is not necessarily required to beprovided on the entire outer circumference of the optical fiber cable 60as long as it provides a desired rigidity to the optical fiber cable 60.Further, the photo-curing resin coating is not necessarily required tobe provided over the entire length of the optical fiber cable 60.

Next, a method of manufacturing the X-ray generating device according tothe present embodiment will be described by using FIG. 5. The X-raygenerating device according to the present embodiment can bemanufactured according to the flow illustrated in FIG. 5.

First, respective components of the X-ray generating device are prepared(step S201).

Subsequently, among the prepared components, those to be accommodated inthe storage container 10 are installed inside the storage container 10(step S202). In this step, the optical fiber cable 60 is installed to apredetermined location in the storage container 10 after a photo-curingresin coating is applied thereto and before this photo-curing resin iscured. Since the optical fiber cable 60 is flexible before thephoto-curing resin is cured, installation of respective components andconnection of the optical fiber cable 60 can be easily made.

Subsequently, the optical fiber cable installed inside the storagecontainer 10 is irradiated with a predetermined energy ray, for examplean ultraviolet ray to cure the photo-curing resin of the coating (stepS203).

Subsequently, the insulating oil 80 is filled in the storage container10 after the photo-curing resin is cured (step S204). It is preferableto apply vacuum impregnation, in which the insulating oil 80 is injectedinto the storage container 10 after evacuating the inside of the storagecontainer 10, to fill the insulating oil 80 in the storage container 10.

By curing the optical fiber cable 60 as discussed above, it is possibleto suppress fluctuation of the optical fiber cable 60 due to aconvective flow of the insulating oil 80 at the operation of the X-raygenerating device and prevent malfunction of the control system.

As discussed above, according to the present embodiment, since therigidity of the optical fiber cable 60 is increased and fluctuation ofthe optical fiber cable 60 due to a convective flow of the insulatingoil 80 is suppressed, malfunction of the control system can be reduced.This allows for a further reduction in size of the X-ray generatingdevice and a further increase in the application voltage.

Fourth Embodiment

An X-ray photography system according to the fourth embodiment of thepresent invention will be described with reference to FIG. 6. FIG. 6 isa block diagram illustrating a general configuration of the X-rayphotography system according to the present embodiment.

In the present embodiment, the X-ray photography system using the X-raygenerating device according to the first to third embodiments isdescribed.

As illustrated in FIG. 6, an X-ray photography system 200 according tothe present embodiment includes the X-ray generating device 100, anX-ray detection device 110, a system control device 120, and a displaydevice 130.

The X-ray generating device 100 is the X-ray generating device of any ofthe first to third embodiments and includes the X-ray tube 20 and anX-ray tube drive circuit 102. The X-ray tube drive circuit 102 includesthe high voltage generation circuit 30, the electron gun drive circuit40, the control unit 50, and the like in the X-ray generating device ofthe first to third embodiments. The X-ray detection device 110 includesan X-ray detector 112 and a signal processing unit 114. The systemcontrol device 120 is responsible for the entire control of the systemincluding the X-ray generating device 100 and the X-ray detection device110. The display device 130 displays image signals processed by thesystem control device 120 on a screen.

The X-ray tube drive circuit 102 of the X-ray generating device 100outputs various control signals to the X-ray tube 20 under the controlby the system control device 120. The emission state of an X-ray emittedfrom the X-ray generating device 100 is controlled by a control signaloutput from the system control device 120.

An X-ray 104 emitted from the X-ray generating device 100 transmitsthrough a subject 106 and is detected at the X-ray detector 112. TheX-ray detector 112 has a plurality of detection elements (notillustrated) and acquires a transmission X-ray image. The X-ray detector112 converts the acquired transmission X-ray image into an image signaland outputs the image signal to the signal processing unit 114. Betweenthe X-ray tube 20 and the subject 106, a slit, a collimator, or the like(not illustrated) may be arranged in order to suppress unnecessary X-rayirradiation.

The signal processing unit 114 performs predetermined signal processingon an image signal under the control by the system control device 120and outputs the processed image signal to the system control device 120.The system control device 120 outputs a display signal to the displaydevice 130 in order to cause the display device 130 to display an imagebased on the processed image signal. The display device 130 displays acaptured image of the subject 106 based on the display signal on thescreen.

As discussed above, according to the present embodiment, the use of theX-ray generating device 100 of the first to third embodiments which iscompact and superior in discharge breakdown voltage characteristics canrealize a reliable X-ray photography system 200 that can stably acquirecaptured images.

Modified Embodiments

The present invention can be modified in various ways without beinglimited to the embodiments described above.

For example, while the grounding scheme of the X-ray tube 20 is an anodegrounding scheme in the first embodiment described above, the groundingscheme of the X-ray tube 20 is not limited to the anode groundingscheme. For example, a neutral point grounding scheme may be employed inwhich a positive high voltage and a negative high voltage are applied tothe anode and the cathode of the X-ray tube, respectively. Further, whenthe optical fiber cable 60 is cured without using a potential differencebetween the electron gun drive circuit 40 and the control circuit 52 asseen in the second and third embodiments, for example, it is notnecessarily required to cause a potential difference to occur betweenthe electron gun drive circuit 40 and the control circuit 52.

Note that any of the embodiments described above is intended to merelyillustrate an embodied example in implementation of the presentinvention, and the technical scope of the present invention is not to beconstrued in a limiting sense by these embodiments. That is, the presentinvention may be implemented in various forms without departing from thetechnical concept thereof or primary features thereof.

What is claimed is:
 1. An X-ray generating device comprising: an X-raytube; a drive circuit that drives the X-ray tube; a voltage generationcircuit that generates an electron acceleration voltage applied to theX-ray tube; and a control unit that communicates with the drive circuitand the voltage generation circuit, wherein at least the X-ray tube, thedrive circuit, and the voltage generation circuit are arranged inside astorage container filled with an insulating oil, wherein at least a partof a path connecting the drive circuit and the control unit is formed ofan optical fiber cable arranged inside the storage container, whereinthe optical fiber cable has a coating that suppresses fluctuation of theoptical fiber cable due to a convective flow of the insulating oilgenerated at driving of the voltage generation circuit, wherein thecoating is cured by, from a resin material containing a plasticizer, atleast a part of the plasticizer being leaching out, and wherein thecontrol unit is configured to facilitate leaching of the plasticizer bydriving the voltage generation circuit to apply a voltage for apredetermined time to the optical fiber cable in a state of no X-raybeing generated.
 2. A method of manufacturing an X-ray generating deviceincluding an X-ray tube, a drive circuit that drives the X-ray tube, avoltage generation circuit that generates an electron accelerationvoltage applied to the X-ray tube, and a control unit that communicateswith the drive circuit and the voltage generation circuit, wherein atleast the X-ray tube, the drive circuit, and the voltage generationcircuit are arranged inside a storage container filled with aninsulating oil, and wherein at least a part of a path connecting thedrive circuit and the control unit is formed of an optical fiber cablearranged inside the storage container, the method comprising: installingthe X-ray tube, the drive circuit, the voltage generation circuit, andthe optical fiber cable inside the storage container; filling theinsulating oil in the storage container, and curing, after filling theinsulating oil in the storage container, a coating of the optical fibercable by driving the voltage generation circuit, without driving thedrive circuit, to apply a voltage for a predetermined time to theoptical fiber cable having the coating of a resin material containing aplasticizer and causing the plasticizer to leach out from the coating.3. An X-ray photography system comprising: the X-ray generating deviceaccording to claim 1; an X-ray detection device that detects an X-raythat has been emitted from the X-ray generating device and hastransmitted through a subject; and a signal processing unit thatconverts a transmission X-ray image of the subject detected by the X-raydetection device into an image signal.